1. Technical Field
The present invention relates to a slide valve, particularly to a slide valve having a body with a pendular plate that is laterally movable in the horizontal direction relative to its flow path axis to cause its valve member to shut off the flow path of its valve port at a fully closed position.
2. Background Art
A slide valve of this kind generally attains its switching and controlling while making a lateral or horizontal movement to move to a fully open position and a fully closed position within a flat hollow valve casing. As a conventional slide valve, there has been proposed a configuration which has mounted on a valve casing an air driving portion for sealing a valve seat, and has installed within the valve casing a detachable seal ring for sealing the valve seat. The configuration causes the seal ring to be pressed against a movable swing plate in a state in which the swing plate has moved to a valve-closing position, thereby enabling the valve seat to be sealed (refer to Patent Document 1). Since Patent Document 1 adopts a structure in which the backing pressure is exerted only to the difference in area between the diameters of an O-ring of the seal ring for sealing the valve seat and a slidable O-ring, it is at an advantage in establishing sealing while bearing a thrust of the pressure difference between the atmospheric pressure and a vacuum with a small valve thrust.
There has also been proposed a slide valve having a structure in which a swing plate is provided on the circumferential portion thereof with convexo-concave parts or grooves to make the controllability of the minimum flow rate good (refer to Patent Document 2). There has been known, as another system for making the controllability good, a valve having a structure having a contact ring attached to a slide plate and, when the slide plate is in a closed position, bringing the contact ring into pressure contact with the contact surface of a body due to the biasing force of a spring (refer to Patent Document 3).
As another conventional example, a gate valve has been proposed, which has a structure wherein a cam using a roller is used to spread a valve element and a plate installed on the back surface of the valve element to the opposite sides when blocking the valve element and press the plate against the inner surface of a body to receive on the plate a load of blocking the valve element, thereby completing the valve blocking (refer to Patent document 4). In this gate valve, the spreading of the valve element and the plate to the opposite sides by the cam causes an O-ring for sealing a valve seat to be pressed, thereby allowing the roller to ride over the horizontal position of the cam. As a result, since a thrust resulting from the pressure difference between the atmospheric pressure and a vacuum is not converted into a force in a valve-opening direction, sealing can be retained.
Patent Document 1: JP-A HEI 9-178000
Patent Document 2: JP-A HEI 9-210222
Patent Document 3: JP-A 2005-9678
Patent Document 4: JP-A 2002-295695